J/A+A/522/A26 Fe Abundances in metal-poor stars (Sbordone+ 2010)
The metal-poor end of the Spite plateau.
I: Stellar parameters, metallicities, and lithium abundances.
Sbordone L., Bonifacio P., Caffau E., Ludwig H.-G., Behara N. T.,
Gonzalez Hernandez J.I., Steffen M., Cayrel R., Freytag B.,
Van't Veer C., Molaro P., Plez B., Sivarani T., Spite M., Spite F.,
Beers T.C., Christlieb N., Francois P., Hill V.
<Astron. Astrophys. 522, A26 (2010)>
=2010A&A...522A..26S 2010A&A...522A..26S
ADC_Keywords: Abundances, [Fe/H] ; Abundances, peculiar ; Stars, population II
Keywords: nuclear reactions - nucleosynthesis - abundances - Galaxy: halo -
Galaxy: abundances - cosmology: observations - stars: Population II
Abstract:
The determination of Lithium abundance A(Li) is extremely sensitive to
the adopted temperature scale, so that a Teff bias might mimic a trend
in A(Li). We present here VLT-UVES Li abundances for 28 halo dwarf
stars between [Fe/H]=-2.5 and -3.5, 10 of which have [Fe/H]←3. Four
different Teff scales have been used: Direct Infrared Flux Method
(IRFM) has been used on the basis of 2MASS infrared photometry;
Hα wings have been fitted against two synthetic grids computed
by means of 1D LTE atmosphere models, and a grid of Hα profiles
computed by means of 3D hydrodynamical atmosphere models.
As a result, we confirm previous claims that A(Li) does not exhibit a
plateau below [Fe/H]=-3. A strong positive correlation with [Fe/H]
appears, not influenced by the choice of the Teff estimator. From a
linear fit, we obtain a strong slope of about 0.30 dex in A(Li) per
dex in [Fe/H], significant to 2-3, and consistent within 1 among all
the four Teff estimators. A significant slope is also detected in the
A(Li)-Teff plane, driven mainly by the coolest stars in the sample
(Teff<6250), which appear Li-poor. However, removing such stars does
not alter significantly the behavior in the A(Li)-[Fe/H] plane. When
the full sample is considered, the scatter in A(Li) increases by a
factor of 2 towards lower metallicities, while the plateau appears
very thin above [Fe/H]=-2.8. At this metallicity, the plateau lies at
A(Li)3D,NLTE=2.199±0.086.
Description:
Line-by-line abundances for FeI and FeII lines used to estimate
metallicity and gravity for the program stars. The first column lists
the star name, then the ion (FeI or FeII) The the wavelength in nm,
the loggf, the measured EW (pm) and the derived abundance assuming
the four stellar parameter sets used in the article, respectively 3D,
BA, ALI and IRFM.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 65 29 List of program stars
table3.dat 75 3010 FeI and FeII abundances of the program stars
table4.dat 119 29 Atmosphere parameters of the program stars
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star name
14- 15 I2 h RAh Right Ascension J2000 (hours)
17- 18 I2 min RAm Right Ascension J2000 (minutes)
20- 23 F4.1 s RAs Right Ascension J2000 (seconds)
25 A1 --- DE- Declination J2000 (sign)
26- 27 I2 deg DEd Declination J2000 (degrees)
29- 30 I2 arcmin DEm Declination J2000 (minutes)
32- 33 I2 arcsec DEs Declination J2000 (seconds)
35- 39 F5.2 mag Vmag ?=- V magnitude
41- 45 F5.2 mag Jmag ?=- 2MASS J magnitude
47- 51 F5.2 mag Hmag ?=- 2MASS H magnitude
53- 57 F5.2 mag Kmag ?=- 2MASS Ks magnitude
59- 65 F7.5 mag E(B-V) ?=- B-V color excess
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star identification
16- 19 A4 --- Ion FeI or FeII ion
23- 30 F8.4 nm lambda Line wavelength
34- 39 F6.3 -- loggf Line oscillator strength
42- 47 F6.2 pm EW Line equivalent width
50- 54 F5.2 -- 3Dabu ?=99.9 Abundance, 3D parameters (G1) (1)
57- 61 F5.2 -- BAabu ?=99.9 Abundance, BA parameters (G1) (1)
64- 68 F5.2 -- ALIabu ?=99.9 Abundance, ALI parameters (1) (G1)
71- 75 F5.2 -- IRFMabu ?=99.9 Abundance, IRFM parameters (1) (G1)
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Note (1): A value of 99.90 indicates that the line has not been used
for this specific star and parameter set.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star name
14- 17 I4 K Teff1 ?=- Effective temperature on the BA scale
21- 24 F4.2 [cm/s2] logg1 ?=- Gravity on the BA scale
29- 31 F3.1 km/s xi1 ?=- Miroturbulence velocity on the BA scale
33- 37 F5.2 [Sun] [Fe/H]1 ?=- Metallicity on the BA scale
40- 43 I4 K Teff2 ?=- Effective temperature on the ALI scale
47- 50 F4.2 [cm/s2] logg2 ?=- Gravity on the ALI scale
56- 58 F3.1 km/s xi2 ?=- Miroturbulence velocity on the ALI scale
60- 64 F5.2 [Sun] [Fe/H]2 ?=- Metallicity on the ALI scale
67- 70 I4 K Teff3 ?=- Effective temperature on the IRFM scale
74- 77 F4.2 [cm/s2] logg3 ?=- Gravity on the IRFM scale
83- 85 F3.1 km/s xi3 ?=- Miroturbulence velocity on the IRFM scale
88- 92 F5.2 [Sun] [Fe/H]3 ?=- Metallicity on the IRFM scale
95- 98 I4 K Teff4 Effective temperature on the 3D scale
102-105 F4.2 [cm/s2] logg4 Gravity on the 3D scale
110-112 F3.1 km/s xi4 Miroturbulence velocity on the 3D scale
115-119 F5.2 [Sun] [Fe/H]4 Metallicity on the 3D scale
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Globale Notes:
Note (G1): the parameters are defined on 4 scales:
BA = temperatures derived from Hα-wing fitting, using 1D atmosphere
models and spectrosynthesis, self broadening (Barklem et al.
2000A&A...355L...5B 2000A&A...355L...5B, 2000A&A...363.1091B 2000A&A...363.1091B) and Stark broadening
(Stehle & Hutcheon, 1999A&AS..140...93S 1999A&AS..140...93S)
ALI = same as BA, but using the self-broadening theory from Ali & Griem
(1966, Physical Review , 144, 366)
3D = same as BA, but using 3D atmosphere models and spectrosynthesis
IRFM = temperature derived with the Infrared Flux Method (see section 4.2
and Gonzalez Hernandez & Bonifacio 2009A&A...497..497G 2009A&A...497..497G)
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Acknowledgements:
Luca Sbordone, lsbordone(at)mpa-garching.mpg.de
(End) Luca Sbordone [MPA], Francois Ochsenbein [CDS] 16-Aug-2010